1. Field of the Invention
The present invention relates to massively parallel computing systems and, more specifically, to computing systems in which computing nodes are interconnected via a Kautz-like topology for data links and which include a control back channel in the opposite direction.
2. Discussion of Related Art
Massively parallel computing systems have been proposed for scientific computing and other compute-intensive applications. The computing system typically includes many nodes, and each node may contain several processors. Various forms of interconnect topologies have been proposed to connect the nodes, including Hypercube topologies, butterfly and omega networks, tori of various dimensions, fat trees, and random networks.
One problem that has been observed with certain architectures is the issue of scalability. That is, due to inherent limitations, certain architectures are not easily scalable in any practical way. For example, one cannot simply add processing power by including another module of computing nodes into the system, or more commonly, the expense and/or performance of the network becomes unacceptable as it grows larger. Moreover, different sized systems might need totally different module designs. For example, hypercube topologies had nodes in which the number of ports or links was dependent on the overall size of the system. Thus a node made for one size system could not be used, as a general matter, on a system with a different size.
Another problem that has been observed is that of routing the connections among nodes. Large systems typically cannot be fully connected because of inherent difficulty in routing. Thus switching architectures have been proposed, but these introduce latency from the various “hops” among nodes that may be necessary for two arbitrary nodes to communicate with one another. Reducing this latency is desirable but has proven difficult.